Trouble Maintaining Free Chlorine after Opening this year

RyeRock23

Member
May 4, 2022
22
Indianapolis, IN
We opened our pool almost 3 weeks ago and have not swam in it yet. Pool company said we lost too much chlorine over the winter and "shocked" it at opening. We only use the company to open/close, I do all the maintenance in between myself. After letting their shock levels come down, I began measuring everything. My CYA was really low, ph was high, alkalinity was high. I balanced my ph and began a SLAM guessing my CYA was around 20 (vial only goes to 30, but I know there had to be some in there from prior year). I maintained FC at or above 12 (yes I know higher than CYA) for about a day and let it go forgetting to do an OCLT. I noticed that the chlorine was dropping way faster than prior years. In fact my FC fell below 2 after 2 days even with pool covered. So I knew I needed to SLAM again and remembered about the OCLT after coming back here to the site for the first time this year. By this point my CYA was at 30 after adding stabilizer so I did a SLAM to at or above 12 and held it. First night OCLT was 2.0 and then second night OCLT was 1.0 (or possibly little less because one drop equaled 0.5). I stopped SLAM.

Here's where the problem continues. I am losing FC like crazy and my SWG isn't maintaining my chlorine levels like it has in the past. It is oversized for our pool size so in past years it ran 10-15% 10 hours/day pump run when cover on/no one swimming, we would bump it up to 20-25% when few swimmers or 35% when 4 or more swimmers. This year it's just not keeping up even when pool is covered and it is set at 25%. In fact I ran it yesterday at 100% for 5 1/2 hours with pool uncovered and I broke even FC 3.5 before I boosted SWG and FC 3.5 after boosting for 5 1/2 hours. Per Pentairs manual, I tested FC well away from SWG and got FC 3.5 and get FC 5.5 from the return so it does seem to be producing chlorine. The metal blades inside the SWG looked really good and no calcium deposit that I could see. Last night with SWG set at 25%, I closed the pool with FC of 3.5 and had a FC of 2.2 today about 16 hours in between tests. Water is really blue/clear, but we do have frequent debris in it as we live right on the edge of wooded preserve area. I vacuum with robot almost twice a day this year. A couple days ago I heated the pool from 67 degrees to 84 degrees over about 7 hours and lost 10ppm FC just doing that.

Since the SWG isn't keeping up and can't seem to find the right setting I've gone through about 5 gallons of shock btwn the SLAMs and maintenance. All my testing reagents from my Taylor 2006C kit have been replaced new this season/none are expired. Out of desperation I took a sample to Leslie's just out of curiosity. My FC reading was 5.5 and CC .4 within minutes of taking the sample for Leslies. Their results showed the following: FC 2.93, CC .4, CYA 27, ph 7.3, alkalinity 140, calcium hardness 172 and phosphates 600. Of course they wanted me to buy Fresh n Clear to address the CC, something to bring up the Calcium and then something to bring down the phosphates. I've read enough of the threads about Fresh n Clear and the classic pool store money maker with phosphates so I'm pretty versed there. She also tried to sell me some new algaecide for $52 just in case, even though there's no visible proof that we have algae at this point.

I left the store feeling pretty deflated and defeated. Why isn't my SWG performing like it has in years past? Why am I losing so much FC and fast? I know my CYA should be higher, but I dumped a gallon of liquid stabilizer in it so far which according to the label should have raised my pool by 40 CYA so I'm baffled why I'm only at 30. How many more times do I need to SLAM and/or is that even what I need to be doing at this point? Should I try an acid wash on my SWG just in case? My salt level is right within specs so that's fine. Should I put in an algaecide just out of desperation? I know treating phosphates around here is generally a no no/waste of money and will make me have to clean my filter cartridges, but should I try it? I've seen conflicting opinions on phosphates having an impact on SWG and in fact Pentair states the following in the manual: "Phosphates can cause extremely high chlorine demands and will deplete chlorine from your swimming pool." "Phosphates should not exceed 125."
 
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I would do another SLAM, and after you pass the OCLT, keep FC at SLAM level for another day or 2 to be absolutely sure.

After that, you can also run an Overnight Chlorine GAIN Test for your SWCG: test FC after sunset , and then set your SWCG to 100% and run it for some period of time that you can use to calculate the affect it should have on your pool, then test again to see if your generator has made the amount that you expect.
 
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Quick update. Been running SWG at 40% trying to find the new balance compared to previous year settings. Ended up with FC of 12 at opening yesterday morning. Left pool open all day with consistent sun exposure. CYA measured roughly between 35-40. Put 48 oz algaecide which falls between the maintenance dose and new water fill dose. Few hours later added dose of naturalchemistry phosfree per instructions for 600ppm Phosphates. It's been 20 hours and no impact to the filter pressure/no cloudiness so I'm not sure if I should clean filters after 48 hour run time or not as instructions indicate to do so. My biggest win is with the OCLT... I closed the pool last night with FC of 10 and 11 hours later opened pool with two FC readings, first one FC of 9.5 and second of 10.0. I'm going to spend the next few days allowing the FC to drop while trying to find a maintenance balance using the SWG around 5 (using CYA range of 3-7).
 
Put 48 oz algaecide which falls between the maintenance dose and new water fill dose. Few hours later added dose of naturalchemistry phosfree per instructions for 600ppm Phosphates
No need for either of these. Read these:

while trying to find a maintenance balance using the SWG around 5
Your SWCG output% and or Pump Run Time will likely vary throughout the year based on usage and sun. You will use the most in June/July. There likely will not be just one setting, set and forget that will work for the entire season.
 
No need for either of these. Read these:


Your SWCG output% and or Pump Run Time will likely vary throughout the year based on usage and sun. You will use the most in June/July. There likely will not be just one setting, set and forget that will work for the entire season.
Thank you for your response and links. Yes, I've read pretty much everything here over the last few years. I get what you're saying, but I haven't found it to be true for my pool and SWG so I'm hoping that by posting if someone else comes along feeling defeated and desperate like me, my course of action may help them or give them some reassurance/patience. Third year opening the pool and something was totally different this year and I still have no clue what. Just know that even after doing a second SLAM and passing an OCLT I was still losing chlorine like crazy. The SWG settings I mentioned in my first post have got us through the entire swim season. Although in cooler temps or less swimming it tends to run the FC a little high. This year, I'm at least double or more of the SWG setting with 24/7 pump run time (previous years was 10 on/14 off) and it wasn't keeping up with the demand despite no swimmers and an auto cover on most/all of the day. I'm not sure if the SWG was slow to start this year, if I just needed to allow time for the CYA to catch up/dissolve, if the sun did it's magic or if the algaecide/phosphate remover had an impact. All I know is that things are improving and I'm hopeful that I'll be able to settle back into the SWG settings we've used the past two swim seasons.
 
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My own SWG wasn't producing much with cool water at opening. I was thrilled when the cold water light went off on day 3, but wasn't seeing much production while the water danced the in the 50s. It didn't matter because I wasn't losing much FC so it was a wash. When the water warmed up to the 60s, production hit expected targets.

IMO you had algae wiping out the reduced production. The low CYA contributed to excessive FC loss as well.

If it happens again, shut the cell off and prove the pool stable for a few days, dosing with LC. Pass a OCLT with flying colors, I personally never trust it on the fence. Then you can do an overnight *gain* test to prove the cell is OK
 
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Also, algecide is entirely counterproductive during the season. Why would you add something for a FC problem, that depletes FC ? Said lost FC depletes said addition, leaving you with less of each. You continue adding FC as you should until the addition is gone. You end up with no more addition and FC lost for no reason. :)

It's for winter use, for folks closing early.
 
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